Planting racks

help! A few yers ago(well many) i bought some round planting racks. They were metal and had about four sets of double rings into which you put small pots of growingseeds. Mine have rotted away and I cannot find a source to replace them-can any one help?

Many thanks for tjhe suggestion;however I think my discription was a bit at fault. My unit was about 4 foot high and had space oin each rings for about 15 pots, about 4.5" across, with fout sets of double rings. Any ideas? And thanks.